Pan-STARRS, ATLAS and optical transient searches

The Pan-STARRS1 survey is collecting multi-epoch, multi-colour observations of the sky north of declination -30 degrees, and has designated 70 deg(2) for nightly observations that are particularly useful for transient detection. A duplicate, Pan-STARRS2, is nearing completion that offers opportunities to improve the quality of transient search and observation, as well as simply increasing the number of detections. A new system, the Asteroid Terrestrial-impact Last Alert System (ATLAS), increases the search area to all-sky in return for diminished sensitivity, and highlights tension among optimization for static sky images, optimization for faint transients and optimization for an unbiased number of transients. ATLAS gives up sub-arcsecond images and full colour information to specialize in the third category, but should detect many more transients than the Pan-STARRS1 Medium Deep fields or the Palomar Transient Factory, with examples of transient classes that are considerably closer and brighter.